Coagulation and Anticoagulation in Extracorporeal Membrane Oxygenation

Abstract

The hemostatic system poses a major problem in extracorporeal membrane oxygenation (ECMO). The foreign surface in the extracorporeal circuit activates platelets and the clotting system. To avoid loss of platelets and activation of the clotting system, anticoagulation is necessary. In addition, in many patients on ECMO, preexisting clotting disorders are present. Therefore, bleeding and/or thrombosis are frequent complications in ECMO patients that require specific treatment and may even necessitate termination of ECMO. Most ECMO centers use heparin for anticoagulation and the activated clotting time (ACT) for monitoring. Reduction of problems with hemostasis may be obtained with less thrombogenic surfaces, new anticoagulants with a short half-life, platelet inhibitors, protease inhibitors, or selective anticoagulation in the extracorporeal circuit. While there will probably never be a complete nonthrombogenic surface available and all anticoagulants will have some risk of bleeding, improvement can be obtained by a combination of measures including better surfaces, more sophisticated anticoagulation regimens, and close laboratory monitoring.

Factors associated with survival in pediatric extracorporeal membrane oxygenation—a single-center experience

“…Hemorrhage (gastrointestinal, cannula site, and surgical site) remains the major problem associated with ECLS and is associated with poorer outcome [37]. Hemorrhagic complications are especially prominent among patients requiring surgery or invasive procedures before ECMO [38,39].…”

The Influence of Free Hemoglobin and Bilirubin on Heparin Monitoring by Activated Partial Thromboplastin Time and Anti-Xa Assay

“…2,3 In order to prevent activation of the hemostatic system into the circuit, unfractionated heparin (UH) is usually administered for patients on ECMO and therapeutic anticoagulation is monitored by various laboratory tests: activated clotting time, activated partial thromboplastin time (aPTT), anti-Xa assay, and thromboelastography. 4,5 Our previous experience in laboratory monitoring of heparin therapy in neonatal ECMO has shown poor correlation among anti-Xa, aPTT, and activated clotting time, suggesting no single laboratory test is useful to determine appropriate anticoagulation management in these settings. 6 Indeed, ECMO support is frequently complicated with mechanical hemolysis followed by elevated plasma free hemoglobin (Hb) and hyperbilirubinemia, 7,8 which could affect the abovementioned assays and affect UH monitoring.…”

Prevention and Treatment of Thrombosis in Pediatric and Congenital Heart Disease

“…Prolongation of the PTT to 1.5 to 2.5 times the control value and an antiFXa level of 0.3 to 0.7 U/mL have been suggested as suitable targets for anticoagulation of patients on ECMO. 499,500 In addition, the ECMO circuit must be visually inspected for clots on a regular basis. For patients who cannot be weaned from CPB, it is reasonable to forego the loading dose of heparin because the patient should already be suitably anticoagulated and additional heparin may increase the risk of bleeding.…”